Astronauts Perform Emergency Spacewalk To Fix Ammonia Leak

On Saturday afternoon, NASA astronauts Chris Cassidy and Tom Marshburn successfully completed a spacewalk to repair a leaky component on the outside of the International Space Station.

A problem with the station was first noted on Thursday, when Station Commander Chris Hadfield noticed a steady stream of ammonia "snowflakes" on the outside of the station. Ammonia coolant is used on the station to regulate the temperature of the power channels coming from the station's 8 solar arrays. Each array has an independent cooling system, so the leak didn't threaten the safety of the station, but could have impacted the amount of power needed to complete its missions.

Using video of the leaks, NASA engineers were able to determine that the leak was coming from one of the system's pumps. So over the course of the day on Thursday and Friday, an emergency spacewalk plan was put together and given the okay by NASA. During that time, the pump to the array was shut down, leaving the station to function on only 7 of its 8 solar arrays.

At 8:44am EDT on Saturday, Astronauts Cassidy and Marshburn powered up their suits and headed outside the station to fix the leak. They did so by replacing the coolant pump. After replacing the pump, it was powered on, and both the astronauts and Mission Control verified that there was no more leaking. After that, the astronauts headed back inside.

With less than 48 hours from start to finish, this marks the shortest period of time it has taken to plan and complete a spacewalk mission.

Next up for some of the station's astronaut is a different mission - heading home. On Sunday at 3:40pm EDT, Commander Chris Hadfield will hand command of the Space Station over to Russian Cosmonaut Pavel Vinogradov. Then on Monday, crew members Hadfield, Marshburn and Roman Romanenko will undock their Russian Soyuz from the station and head back to Earth for a planned 10:31pm EDT landing in Kazakhstan.